How can I fix my NTFS partition?

[oldfred]

I also found out that there are differences. And chkdsk from Windows 7 on a XP partition will convert it.

I used a Windows 7 repair CD to run chkdsk on my XP partition. It did find additional errors. But it converted the NTFS PBR - partition boot sector to the new version. In Testdisk you can compare (dump) the backup PBR to the active PBR and in plain text was bootmgr (for Vista/7) on current and ntldr (for my XP) on backup. I had to restore backup.
Or you can use the "bootsect.exe /nt52 c:" command to restore an XP PBR.

[mikesena]

So! I gave up on the whole thing and after buying a new external drive and backup the data, went to install Windows again fresh (still need to dual boot). Windows STILL couldn't pick up the drive. That's when I got suspicious.

1. I went into gparted (eyeballs above conversation)
2. Deleted the mount that I'd attempted to create in Windows
3. REsized the drive back to what it was before.
4. Rebooted.
5. Windows asked whether I wanted to recover Windows (instead of booting normally)
6. THIS TIME, it actually seemed to do something.
7. Rebooted, and all was well.

Thanks to the advice from all. Turns out even undo'ing what you've done with partitions can sometimes fix issues.